Communications devices and methods for selecting a wireless access interface

ABSTRACT

A communications device transmits data to a mobile communications network or receives data from a mobile communications network. The mobile communications network includes plural infrastructure equipment each providing a wireless access interface for the communications device. The wireless access interfaces may have a different frequency but operate in accordance with the same standard or may use different radio access technologies. The communications device selects one of the wireless access interface by generating a signal reception metric for each of the wireless access interfaces provided by the one or more neighbouring infrastructure equipment and each if the wireless access interfaces provided by the selected infrastructure equipment, and selects or reselects one of the wireless access interfaces provided by the one or more neighbouring infrastructure equipment or one of the wireless access interfaces provided by the selected infrastructure equipment in accordance with predetermined criteria based on the generated signal reception metrics.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/133,528, filed Sep. 17, 2018, which is a continuation of U.S.application Ser. No. 15/113,691, filed Jul. 22, 2016 (now U.S. Pat. No.10,091,722), which is based on PCT filing PCT/EP2014/079339, filed Dec.24, 2014, and claims priority to European Patent Application 1415396.7,filed in the European Patent Office on Feb. 7, 2014, the entire contentsof each of which being incorporated herein by reference.

TECHNICAL FIELD OF THE DISCLOSURE

The present disclosure relates to communications devices and methods forcommunicating data using communications devices, and in particular tocommunications devices which are configured to perform device-to-devicecommunications.

BACKGROUND OF THE DISCLOSURE

Third and fourth generation mobile telecommunication systems, such asthose based on the 3GPP defined UMTS and Long Term Evolution (LTE)architecture are able to support more sophisticated services than simplevoice and messaging services offered by previous generations of mobiletelecommunication systems.

For example, with the improved radio interface and enhanced data ratesprovided by LTE systems, a user is able to enjoy high data rateapplications such as mobile video streaming and mobile videoconferencing that would previously only have been available via a fixedline data connection. The demand to deploy third and fourth generationnetworks is therefore strong and the coverage area of these networks,i.e. geographic locations where access to the networks is possible, isexpected to increase rapidly.

The anticipated widespread deployment of third and fourth generationnetworks has led to the parallel development of a class of devices andapplications which, rather than taking advantage of the high data ratesavailable, instead take advantage of the robust radio interface andincreasing ubiquity of the coverage area. Examples include so-calledmachine type communication (MTC) applications, which are typified bysemi-autonomous or autonomous wireless communication devices (i.e. MTCdevices) communicating small amounts of data on a relatively infrequentbasis. Examples include so-called smart meters which, for example, arelocated in a customer's house and periodically transmit information backto a central MTC server data relating to the customers consumption of autility such as gas, water, electricity and so on. Other examplesinclude medical devices and automotive applications in which measurementdata is gathered from sensors on a vehicle and transmitted via a mobilecommunications network to a server attached to the network.

Unlike a conventional third or fourth generation communications devicesuch as a smartphone, an MTC-type terminal is preferably relativelysimple and inexpensive, having a reduced capability. It is usuallyjustified to include complex transceivers in a smartphone because asmartphone will typically require a powerful processor to performtypical smartphone type functions. However, a desire to use relativelyinexpensive and less complex devices to communicate using LTE typenetworks may result in a receiver of such a device to be less sensitiveto detect and to recover data from received signals or a transmitter maybe less powerful. Furthermore, MTC devices may deployed in locationswhere it may be more difficult for radio signals to reach the device,for example, in a situation in which a communications device such as asmart meter is deployed in the basement of a house.

In order to improve a likelihood that radio signals may be received by alow cost communications device or from a low cost communications device,it has been proposed to deploy a so called extended coverage cell or anenhanced wireless access interface. Cell enhancement or extension is atechnique which is being proposed for example for LTE Standards whichprovides an arrangement of effectively extending a coverage area of abase station or eNodeB to reach a communications device which may beotherwise out of a coverage area. Coverage extension is achieved byemploying a wireless access interface enhancement techniques such asboosting the power of certain signals or transmitting control signals ordata repeatedly, effectively a coverage area of the base station can beextended.

In a scenario in which a communications device must select or reselect awireless access interface provided by a base station to form a cell of amobile communications system, it will be appreciated that there may beoccasions when it is appropriate to select an extended coverage cell,whereas in other situations the extended coverage cell may not providean optimum use of communications resources.

SUMMARY OF THE DISCLOSURE

According to a first aspect there is provided a method of selecting awireless access interface for transmitting data from a communicationsdevice to a mobile communications network or receiving data from amobile communications network at a communications device. The mobilecommunications network includes a plurality of infrastructure equipmenteach providing one or more wireless access interface for thecommunications device. The wireless access interfaces may be wirelessaccess interfaces operating in accordance with the same transceivertechniques (same radio interface standard) on the same or differentfrequencies or different radio access technologies. The wireless accessinterfaces may be provided by different infrastructure equipment andtherefore different cells of the mobile communications network. Themethod comprises selecting, by the communications device, one of thewireless access interfaces of the infrastructure equipment as a servingwireless access interface. One or more of the selected infrastructureequipment or one or more neighbouring infrastructure equipment providean enhanced wireless access interface providing a facility fortransmitting or receiving the signals at a lower power relative to awireless access interface which is not enhanced. The selecting the oneof the wireless access interface comprises generating a signal receptionmetric for each of the wireless access interfaces provided by the one ormore neighbouring infrastructure equipment and for each of the wirelessaccess interfaces provided by the the selected infrastructure equipment,and selecting or reselecting one of the wireless access interfacesprovided by the one or more neighbouring infrastructure equipment or oneof the wireless access interfaces provided by the selectedinfrastructure equipment in accordance with predetermined criteria basedon the generated signal reception metrics.

Embodiments of the present technique provide an arrangement in which acommunications device selects a wireless access interface or cell, whichmay include an enhanced wireless access interface providing an extendedcell coverage by treating the enhanced wireless access interface as ifthis were another cell, even if the enhanced wireless access interfaceis provided by the same infrastructure equipment a not enhanced wirelessaccess interface. In some examples the enhanced wireless accessinterface may be provided by the selected infrastructure equipment sothat measurements are performed of the enhanced wireless accessinterface and the serving wireless access interface from the same celland evaluated in dependently for selection in accordance with thepredetermined criteria.

Various further aspects and features of the present disclosure aredefined in the appended claims and include a communications device, amethod of receiving data using a communications device, a mobilecommunications network, an infrastructure equipment and a method oftransmitting data from a mobile communications network.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present disclosure will now be described by way ofexample only with reference to the accompanying drawings wherein likeparts are provided with corresponding reference numerals and in which:

FIG. 1 provides a schematic diagram illustrating an example of aconventional mobile telecommunication network;

FIG. 2 provides a schematic diagram illustrating a communications device(UE) communicating with different radio access interfaces according to aheterogeneous radio access network;

FIG. 3 provides a schematic diagram illustrating different coverageareas of different base stations and access points of the heterogeneousradio access network of FIG. 2;

FIG. 4 provides a schematic diagram illustrating an effect of providingan enhanced wireless access interface to an infrastructure equipmentwhich also includes a not enhanced wireless access interface;

FIG. 5 provides a schematic block diagram of a communications device(UE) performing a selection process according to the present techniqueion which one or more of a neighbouring infrastructure equipment or aserving infrastructure equipment may provide an enhanced wireless accessinterface;

FIG. 6 provides an example flow diagram providing an illustration of apreviously proposed process for performing cell reselection;

FIG. 7 provides an example flow diagram providing an illustration of aprocess for performing cell reselection in accordance with the presenttechnique;

FIG. 8 provides an illustrative representation of graphical plots ofsignal reception metrics against time for different wireless accessinterfaces provided by a selected and a neighbouring infrastructureequipment, in which an enhanced wireless access interface of aneighbouring infrastructure equipment is selected; and

FIG. 9 provides an illustrative representation of graphical plots ofsignal reception metrics against time for different wireless accessinterfaces provided by a selected and a neighbouring infrastructureequipment, in which reselection is performed from an enhanced wirelessaccess interface.

DESCRIPTION OF EXAMPLE EMBODIMENTS Example of an LTE System

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a conventional mobile telecommunications network, usingfor example a 3GPP defined UMTS and/or Long Term Evolution (LTE)architecture.

The network includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell) within which data can be communicated to and from communicationsdevices (also referred to as mobile terminals, MT or User equipment, UE)104. Data is transmitted from base stations 101 to communicationsdevices 104 within their respective coverage areas 103 via a radiodownlink. Data is transmitted from communications devices 104 to thebase stations 101 via a radio uplink. The core network 102 routes datato and from the terminal devices 104 via the respective base stations101 and provides functions such as authentication, mobility management,charging and so on.

Mobile communications systems such as those arranged in accordance withthe 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency division multiplex (OFDM) based interface for theradio downlink (so-called OFDMA) and the radio uplink (so-calledSC-FDMA). Further information on the structure and functioning of thephysical channels of LTE systems can be found in [6].

UE Cell Selection

In mobile communication systems it is conventional for a mobilecommunications device (UE) to select a base station or eNodeB throughwhich to transmit and receive signals. For mobile communications systemssuch as LTE, for example, a UE transmits data to and from an eNodeB of amobile communications network and hands over between different eNodeB'sthroughout the mobile radio network as the UE moves in and out of acoverage area provided by the eNodeBs. Within the coverage area thesignal strength of transmitted and received radio signals are sufficientdetectable by the eNodeB and the UE respectively and accordingly the UEcan transmit and receive data to or from that eNodeB. The UE transmitsand receives data from the eNodeB when in an active mode. However, whenin an idle mode then the UE is responsible for selecting which eNodeBand therefore cell to attached to. As such when the UE enters an activemode, for example in order to receive data if the network receives datafor transmission to the UE or if the UE wishes to transmit the data tothe mobile communications network in which case.

The present disclosure concerns techniques for the UE to select anappropriate access point or base station such as an eNodeB to attach toin order to transmit and receive radio signals via that eNodeB. However,the base station or access point to which the UE can attach does notnecessarily conform to a particular radio access standard. Therefore,the base station or access point may not be an eNodeB. Therefore, forsome examples the UE may attach to a WiFi access point or WiMax or otherradio access technology to transmit and receive signals from a mobilecommunications network. As will be explained shortly a complicationarises in selecting an appropriate base station or access point wherefor example an LTE system deploys an enhanced carrier in which thewireless access interface is configured to transmit and to receivesignals to a UE at a lower transmitted and received signal power. Thus,for example, by repeating some control signals transmitted by the eNodeBon the downlink, effectively an extension of the coverage of the cellcan be achieved.

FIG. 2 illustrates a heterogeneous arrangement of wireless accessinterfaces which a UE could attach to. As shown in FIG. 2 a UE 104 cantransmit and receive signals to the eNodeB's 101 within a coverage areaprovided by each of the eNodeB's 101. For the example shown in FIG. 2,the UE 104 is currently attached to an eNodeB 201 which forms a servingeNodeB or serving cell for the UE 101. Also shown in FIG. 2 are twoaccess points 210 which for example operate to provide a wireless accessinterface in accordance with the WiFi standard. Thus the UE 104 mayhandover or reattach to one of the WiFi access points 210 by performinga selection process and selecting the wireless access points 210 insteadof the serving eNodeB 201.

As shown in FIG. 3, each of the base stations or access points shown inFIG. 2 has a coverage area which can be represented as a boundary line301 which surrounds each of the eNodeB's 201, 101 or the access point210. The boundary line 301 represents a illustrative way of explaining acoverage area provided respectively by each of the base stations(eNodeBs) or access points shown in FIG. 2 within which the UE cantransmit and receive signals with that base station or access point tothe extent that data can be transmitted or received. As shown in FIG. 3,the UE 104 may be within a coverage area 301 of more than of theeNodeB's 201, 101 or the access point 210 and therefore must selectwhich of those base stations or access points to attach to fortransmission and reception of signals including access stratum andnon-access stratum data.

Coverage Extension or Enhancement

Coverage enhancement or extension is a technique which is being proposedfor LTE Standards which provides an arrangement of effectively extendinga coverage area of a base station or eNodeB to reach UE's which may beotherwise out of a coverage area. An example application is where a UEsuch as a machine to machine device is disposed in a basement or in anenvironment in which radio signals may find it difficult to penetrateand therefore the UE might be outside of the coverage area of theeNodeB. Therefore, for example in FIG. 4, a conventional coverage areais represented by a dash line 401 whereas UE 402 is outside of thecoverage area of the eNodeB 404. However, by employing a wireless accessinterface enhancement techniques such as boosting the power of certainsignals or transmitting control signals or data repeatedly, effectivelya coverage area of the eNodeB 404 can be extended to a second boundaryline 406. Accordingly, the UE 402 is then within the coverage area ofthe enhanced wireless access interface provided by the eNodeB 404.

FIG. 5 shows an example illustration of the arrangement based on FIG. 3in which the UE is within a coverage area of several base stations oraccess points such as the eNodeB's 201, 101 and the WiFi access point210. However, as shown by the dashed line 410 the serving eNodeB 201also provides an enhanced wireless access interface and therefore thecoverage area of the serving eNodeB is extended to boundary line 410. Acorresponding example is shown by the eNodeB 501 which also includes anenhanced wireless access interface as well as conventional wirelessaccess interface. For the enhanced wireless access interface thecoverage is extended to a dashed line 412. The dashed line thereforeextends the coverage area provided by the eNodeB 501. The UE 104 istherefore able to communicate with the eNodeB 501 via the enhancedwireless access interface but not the wireless access interface whichhas a closer boundary 301 which falls before the UE 104.

As shown in FIG. 5 the UE 404 includes a controller 508 which isarranged to control a receiver 510 and a transmitter 512 in accordancewith the operations of the present technique defined in the followingparagraphs.

Currently the low cost and enhanced coverage work item is beingdiscussed in 3GPP, for example in [1]. One of the two main objectives ofthe enhancement of wireless access interface is as follows:

-   -   Provide a relative LTE coverage improvement—corresponding to 15        dB for FDD—for the UE category/type defined above and other UEs        operating delay tolerant MTC applications with respect to their        respective nominal coverage.        -   Specify the following techniques (which shall be applicable            for both FDD and TDD) to achieve this:            -   Simplification of PHICH and PCFICH functionality or                alternative mechanism to PHICH and PCFICH functionality                so that coverage limited UE is not constrained by PHICH                and PCFICH physical channels            -   A mechanism(s) to support scalability of spectral                efficiency impact for coverage improvement by                identifying UE requiring additional coverage improvement                and informing eNB the amount of coverage the UE                requires.            -   Repetition/TTI bundling and extension to PSD boosting                for applicable channels/signals identified during study                phase.            -   A relaxed requirement for “probability of missed                detection” for PRACH.

The present technique concerns a situation in which a UE performs aselection of a base station or access point to which it should attachfor transmitting and receiving signals. In accordance with somedeployments of mobile communications systems such as LTE, there is thepossibility of transmitting via different frequencies within an LTEnetwork on different frequency divided carriers or using different radioaccess technologies (RAT). Therefore in the following description theterm “wireless access interface” is used to encompass both a differentradio access technology as well as a different wireless access interfaceprovided by a different base station or access point or a wirelessaccess point on a different frequency. Those familiar with LTE willunderstand that the different frequencies and radio access technologiesare provided with a different priority and as part of the cellreselection process the UE is biased to select a wireless accessinterface with a higher priority in accordance with operator policy.This is achieved by transmitting for example the different prioritiesfor the different wireless access interfaces to the UE from the network.However, because a wireless access interface, which has been coverageextended provides a signal reception metric which is biased to a lowervalue because of the coverage extension of the cell, a UE may be morelikely to select an enhanced wireless access interface providing acoverage extension cell whereas a conventional wireless access interfacemay also be selectable. Since the data rates and facilities provided byan extended wireless access interface may be lower than that provided bya wireless access interface in a conventional form which is not enhancedor extended then the UE may inadvertently always select the enhancedwireless access interface whereas it should continue or select aconventional wireless access interface. This problem will be explainedin more detail in the following paragraphs.

As background information references [2], [3], [4] and [5] provideprevious proposals concerning the selection of the enhanced wirelessaccess interface.

According to one example proposal a minimum suitability level isbroadcast by the network in order that the UE may camp on a cell whichhas a lower than measured power/interference (RSRP/RSRQ) at the UE. Thisis possible due to the enhanced coverage operation, which is likely tobe achieved mainly by repetition and combining of uplink and downlinkdata. However, it is also desirable to define a method for prioritisingreselection to cells which are suitable under normal operation, overthose which require coverage enhancements to be suitable. The mainreason for this, which is perhaps not clear from the above references,is that it is possible that a UE which is currently using a cell innormal operation (i.e. non-enhanced coverage) will reselect to anothercell on a higher priority frequency that meets the criteria only due tothe lower suitability level. Obviously, it is beneficial for the UE tobe using a cell in relatively good coverage conditions rather than poor(and enhanced) coverage. The current cell reselection criteria ensuresthis in normal circumstances, however does not take into accountpotential coverage enhancements.

Cell Selection Process

Part of the cell selection process includes a procedure for performing acell measurement procedure. The current cell reselection measurementrules, and the cell reselection criteria are defined in TS36.304 [5].According to an example known selection process a UE may camp (select orreselect) a base station or cell only when the suitability criteria S(cell selection criteria) is met. One example of a cell suitabilitycriteria is provided in TS 36.304, which is summarized as follows:

The cell selection criterion S is fulfilled when:

-   -   Srxlev>0 AND

Squal>0

where:

-   -   Srxlev=Q_(rxlevmeas)−(Q_(rxlevmin)+Q_(rxlevminoffset))−Pcompensation    -   Squal=Q_(qualmeas)−(Q_(qualmin)+Q_(qualminoffset))

Srxlev Cell selection RX level value (dB) Squal Cell selection qualityvalue (dB) Q_(rxlevmeas) Measured cell RX level value (RSRP)Q_(qualmeas) Measured cell quality value (RSRQ) Q_(rxlevmin) Minimumrequired RX level in the cell (dBm) Q_(qualmin) Minimum required qualitylevel in the cell (dB) Q_(rxlevminoffset) Offset to the signalledQ_(rxlevmin) taken into account in the Srxlev evaluation as a result ofa periodic search for a higher priority PLMN while camped normally in aVPLMN [5] Q_(qualminoffset) Offset to the signalled Q_(qualmin) takeninto account in the Squal evaluation as a result of a periodic searchfor a higher priority PLMN while camped normally in a VPLMN [5]Pcompensation max(P_(EMAX) − P_(PowerClass), 0) (dB) P_(EMAX) Maximum TXpower level an UE may use when transmitting on the uplink in the cell(dBm) defined as P_(EMAX) in [TS 36.101] P_(PowerClass) Maximum RFoutput power of the UE (dBm) according to the UE power class as definedin [TS 36.101 ]

Since cells supporting coverage enhancement need to support UEsoperating at lower powers (E.g. 15 dB lower downlink and/or uplinkpower) then the minimum RX level (Qrxlevmin) and quality (Qqualmin)criteria need to be updated to be used only for UEs using the cell inenhanced coverage mode.

Currently the cell selection algorithm used by a UE is left mainly toimplementation, the specification just requires that when the UE finds asuitable cell and it is the best cell on the frequency, then that cellwill be selected.

One very simple implementation will scan all the supported frequenciesin order and will choose a cell on the first frequency, which it finds asuitable cell. More intelligent implementations may use storedinformation to determine the order which frequencies are searched. Forcell selection, one of two approaches can be used

-   -   1) The UE may first search for a suitable cell to camp on,        without coverage enhancement, then will try for coverage        enhancement cells.    -   2) No changes—UE just camps on a cell if it is suitable (even if        in coverage enhancement mode)

The problem with (1) is that it can take a long time to scan all thepossible supported frequencies before determining the UE should camp ona cell using coverage enhanced mode. This can drain UE power as well asdelay UE obtaining service.

For the solution (2) the UE may select a coverage enhancement cellbefore a cell with better coverage, if it using a relatively simple cellselection algorithm. However more intelligent algorithms may overcomethis problem. However the UE will then start using the power savingrules defined for cell reselection. If the cell reselection rules workcorrectly then the UE will find the normal coverage cell relativelyquickly.

Cell Reselection Measurement Rules

The UE applies power saving rules when determining what measurements toperform for cell reselection. The UE shall search for higher priorityfrequencies relatively infrequently when the current cell measurementsare above a threshold (known as service based measurements in order toobtain a higher priority frequency which may provide better service). Ifthe current cell measurement drops below a threshold then the UEadditionally measures equal and lower priority frequencies, as well asperforming these much quicker according to tighter requirements, whichis also known as coverage based measurements, because measuring morequickly it is more likely that a coverage area may be kept.

As previously made proposal is provided in TS36.304 [1], which providesrules to be used by the UE to limit needed measurements:

-   -   If the serving cell fulfils Srxlev>S_(IntraSearchP) and        Squal>S_(IntraSearchQ), the UE may choose not to perform intra        frequency measurements.    -   Otherwise, the UE shall perform intra frequency measurements.    -   The UE shall apply the following rules for E-UTRAN        inter-frequencies and inter-RAT frequencies which are indicated        in system information and for which the UE has priority:        -   For an E-UTRAN inter-frequency or inter-RAT frequency with a            reselection priority higher than the reselection priority of            the current E-UTRA frequency the UE shall perform            measurements of higher priority E-UTRAN inter-frequency or            inter-RAT frequencies.        -   For an E-UTRAN inter-frequency with an equal or lower            reselection priority than the reselection priority of the            current E-UTRA frequency and for inter-RAT frequency with            lower reselection priority than the reselection priority of            the current E-UTRAN frequency:            -   If the serving cell fulfils Srxlev>S_(nonIntraSearchP)                and Squal>S_(nonIntraSearchQ), the UE may choose not to                perform measurements of E-UTRAN inter-frequencies or                inter-RAT frequency cells of equal or lower priority.            -   Otherwise, the UE shall perform measurements of E-UTRAN                inter-frequencies or inter-RAT frequency cells of equal                or lower priority.

Cell Reselection Criteria

In addition to the measurement rules, a number of reselection criteriaare given. In summary, the UE shall reselect to a higher priorityfrequency, if that frequency meets a threshold, and regardless of thecurrent cell measurements. For lower priority frequencies the UE shallreselect if that target frequency meets a threshold, but only if theserving cell is below another threshold (mirroring the measurementrules). For equal priority frequencies the UE performs ranking andselects the highest ranked cell across the frequencies.

An example of a known proposal from TS36.304 [1] for cell reselection toa cell on a higher priority E-UTRAN frequency or inter-RAT frequencythan the serving frequency is performed if

-   -   A cell of a higher priority RAT/frequency fulfils        Srxlev>Thresh_(X, HighP) during a time interval        Treselection_(RAT);

cell reselection to a cell on a lower priority E-UTRAN frequency orinter-RAT frequency than the serving frequency shall be performed if:

-   -   The serving cell fulfils Srxlev<Thresh_(Serving, LowP) and a        cell of a lower priority RAT/frequency fulfils        Srxlev>Thresh_(X, LowP) during a time interval        Treselection_(RAT);

Intra-Frequency and Equal Priority Inter-Frequency Cell ReselectionCriteria

The cell-ranking criterion R_(s) for serving cell and R_(n) forneighbouring cells is defined by:

R _(s) =Q _(meas,s) +Q _(Hyst)

R _(n) =Q _(meas,n) −Qoffset

where:

Q_(meas) RSRP measurement quantity used in cell reselections. QoffsetFor intra-frequency: Equals to Qoffset_(s, n), if Qoffset_(s, n) isvalid, otherwise this equals to zero. For inter-frequency: Equals toQoffset_(s, n) plus Qoffset_(frequency), if Qoffset_(s, n) is valid,otherwise this equals to Qoffset_(frequency).

The cells shall be ranked according to the R criteria specified above,deriving Q_(meas,n) and Q_(meas,s) and calculating the R values usingaveraged RSRP results.

If a cell is ranked as the best cell the UE shall perform cellreselection to that cell.

According to the above explanation, a previously proposed arrangementfor the UE to select a cell or wireless access interface is presented inFIG. 6. FIG. 6 provides a flow diagram for one example implementation ofperforming cell reselection, which is summarised as follows:

S1: The UE performs measurements according to cell reselectionmeasurement rules such as determining the parameter Srxlev identifiedabove, which provides a signal reception metric for existing cells andany neighbouring cells which use different radio access technologies(RAT) and or different frequencies. Effectively these are thereforedifferent wireless access interfaces in accordance with the expressionsused above. In some examples, the UE is configured to measure the signalreception metric (Srxlev or Squal) for higher priority wireless accessinterfaces on an ongoing basis, and only after there are no higherpriority wireless access interfaces with a signal reception metricgreater than a threshold, does the UE measure the signal receptionmetric for lower priority wireless access interfaces. The UE receives afirst threshold (TheshX,HighP) which is the threshold for changing to ahigher priority base station and receives a second threshold which isassociated with reselecting a lower priority wireless access interface.The UE also receives a priority level for each of the wireless accessinterfaces that is for the neighbouring infrastructure equipment and theserving of an infrastructure equipment.

S2: If the signal reception metric (Srxlev, Squal) is above the firstthreshold (TheshX,HighP) associated with switching to a higher prioritywireless access interface then processing proceeds to step S4 otherwiseprocessing proceeds to S6.

S4: If the signal reception metric (Srxlev, Squal) for a higher prioritywireless access interface is above the first threshold (TheshX,HighP)then the UE switches by reselecting the higher priority cell whichbecomes the new serving cell.

S6: If the signal reception metric (Srxlev, Squal) is below the firstthreshold then the UE begins to perform measurements of any wirelessaccess interface including neighbouring cells which have a lowerpriority or an equal priority. The UE therefore determines the signalreception metric (Srxlev, Squal) for lower priority cells and comparesthese with the second threshold (Theshserving,LowP) for selecting thelower priority cells.

S8: If the serving cell has a signal reception metric (Srxlev, Squal),which is below the threshold (Theshserving,LowP) for selecting a lowerpriority wireless access interface then processing proceeds to S9.Otherwise the processing proceeds back to step S1 to performmeasurements again.

S9: If the measured signal reception metric (Srxlev, Squal) for anyother wireless access interface for a neighbouring cell is above thethird threshold (TheshX,LowP) for selecting a lower priority cell thenprocessing proceeds to step S12. Otherwise processing proceeds to stepS10, although processing according to step S10 may in otherillustrations occur in parallel or even before S9.

S10: If the wireless access interfaces are of equal priority then the UEperforms a ranking of the relative order of priority of the wirelessaccess interfaces, which is may select as mentioned above. Processingthen proceeds to step S1.

S12: If the signal reception metric (Srxlev, Squal) is above the thirdthreshold (TheshX,LowP) then the UE selects the lower priority cell asits new cell and the neighbouring cell becomes a serving cell.

Cell Reselection with Enhanced Wireless Access Interface (Cell)

As will be appreciated for the explanation above the flow diagram forselecting a different cell or a wireless access interface is based on anarrangement in which the serving and the neighbouring cells do notinclude an enhanced wireless access interface which may exist either ina neighbouring cell or the serving cell in addition to a conventionalwireless access interface. Therefore the present technique has beendevised as a way of selecting the enhanced wireless access interfaceonly where the signal strength or coverage provided by wireless accessinterface, which is not enhanced i.e. a conventional wireless accessinterface is not selected.

The problem is that the absolute cell reselection criteria (forinter-freq reselection to higher or lower priority frequencies) uses themeasurement quantity which is compared against the thresholds is thesame criteria used for cell selection criteria and which is derived fromthe minimum suitability levels:

Srxlev=Q _(rxlevmeas)−(Q _(rxlevmin) +Q _(rxlevminoffset))−Pcompensation

Squal=Q _(qualmeas)−(Q _(qualmin) +Q _(qualminoffset))

This means that when the Qrxlevmin or Qqualmin is set to a lower valuein order to extend coverage, it also has the effect of making Srxlevhigher. As such, the reselection thresholds which are set for normal UEscan be reached more easily. This causes two problems:

-   -   1) Cell reselection from good coverage to bad coverage: The UE        may be camped on a cell which is not using enhanced coverage        *(either because cell does not support this, or cell level is        good enough that this mode is not enabled). The UE will be        periodically measuring for higher priority frequencies. The UE        may detect a cell on a higher priority frequency that would not        normally meet the cell reselection criteria, however due to the        modified Srxlev calculated with the modified Qrxlevmin, the cell        reselection criteria is met, meaning the UE reselects from a        good coverage cell to a cell which can operate only with        coverage enhancements.    -   2) Preventing reselection from bad coverage to good coverage:        Once the UE has camped on the enhanced coverage cell, the UE        will not perform inter-frequency measurements on equal or lower        priority frequencies (since modified Srxlev means measurements        are not required), or will not reselect even if measurements are        done (since modified Srxlev means the serving cell quality is        still above the threshold). So even if there is another        potential cell which is in good coverage conditions the UE will        not select it.

According to some examples, this is not a problem for intra-frequency orinter-frequency reselection to equal priority layers, since ranking isbased on Qmeas which does not account for Qrxlevmin.

According to the present technique, for each frequency and/or individualcell which supports enhanced coverage mode, the UE may use two prioritylevels, and two thresholds, and evaluates these in parallel as if thesewere actually two different cells/frequencies.

Obtaining threshold and priority values:

Using Srxlev measurements as an example (the same will also apply toSqual):

Option 1:

As mentioned above, it's likely a new Qrxlevmin is needed to decreasethe minimum cell suitability threshold. This automatically will providean additional metric to use for comparison with the provided thresholds.

Srxlev=Q _(rxlevmeas)−(Q _(rxlevmin) +Q _(rxlevminoffset))−Pcompensation

Srxlev,enhanced=Q _(rxlevmeas,enhanced)−(Q _(rxlevmin) +Q_(rxlevminoffset))−Pcompensation

So the UE will always receive the existing Qrxlevmin. If the UE alsoreceives Qrxlevmin,enhanced (the new lower minimum suitability) for thecurrent cell or a neighbour freq/cell then this indicates that enhancedcoverage is supported on the freq/cell and the UE can derive the twothresholds (rather Srxlev values) from this information.

The UE also receives a priority per wireless access interface(frequency). This can be set to any value between 0-7 and shall be usedin conjunction with the existing thresholds.

The Srxlev,enhanced can use an implicit priority with a value −1(similar to the rule used for CSG cells—the priority is considered to belower than any of the configured priorities).

According to the present technique two thresholds and two priorities.The existing threshold and priority used for normal coverage UEs willremain the same and the behaviour does not change. The threshold usingenhanced coverage may be coupled with a lower priority and be evaluatedin addition to the existing priority and threshold as if it was aseparate cell.

According to the present technique therefore:

-   -   The UE will not reselect a higher priority frequency which is        accessible only with enhanced coverage, because that modified        threshold is coupled with lower priority.    -   The UE camped on an enhanced coverage cells will consider all        other cells as higher priority, and so will measure relatively        infrequently which has the effect of saving power as well as        enabling some measurements and reselections to other layers        which may provide better coverage. The UE would then reselect to        another enhanced coverage cell only using ranking (equal        priority inter-frequency or intra-frequency reselection) and        only when the level drops below the modified threshold of the        current frequency.

Option 2:

According to this example, for each wireless access interface, thethreshold and the priority are explicitly signalled. According to thisexample the mobile communications network explicitly signals additionalpriorities, or additional thresholds for each wireless access interface(frequency or individual cell, if some cells on a frequency supportenhanced coverage and others do not). The resulting behaviour is thesame, that these are evaluated in parallel (so two thresholds, and twopriorities per frequency/cell).

One potential way to achieve this is to remove the restriction given insystem information block type 5: “E-UTRAN does not configure more thanone entry for the same physical frequency regardless of the E-ARFCN usedto indicate this.”

However this may cause legacy UEs to interpret that as an error, so itis likely not a useful option.

Use of Threshold and Priority Values

There are several options but the simplest would be to maintain aneighbour list (typically the UE would implement a list of neighbourfrequencies and/or cells along with the specific associated informationsuch as threshold, Qrxlevmin, priority, etc). The UE would just generatean additional entry for each neighbour cell and store the new thresholdand priority parameters (so there are two entries for this cell, withtwo different priority/thresholds). Then cell reselection would work asnormal.

Other implementations may include storing both values for threshold andpriority associated with that wireless access interface (cell orfrequency), and selecting the correct value. For example when performingmeasurement for higher priority layers (service based measurement), theoriginal values will be used, but when doing coverage based measurementthe new values could be applied after checking if the original valuesmeet the cell reselection criteria and this failed.

A flow diagram summarising the operation of a UE to perform the cellselection according to the present technique, which is based on the flowdiagram of FIG. 6, is provided in FIG. 7. The flow diagram of FIG. 7 issummarised as follows:

S20: The UE performs measurements according to cell reselectionmeasurement rules such as determining the parameter Srxlev and/or Squalidentified above, which provides a signal reception metric for existingcells and any neighbouring cells which use different radio accesstechnologies (RAT) and or different frequencies. In some examples themeasurements are performed only for higher priority wireless accessinterfaces first, and then only if a higher priority wireless accessinterface is not selected. The UE then derives a first threshold(ThreshX,HighP) which is the threshold for changing to a higher prioritybase station or access point and a second threshold (Threshserving,LowP)which is associated with reselecting a lower priority wireless accessinterface. The UE also receives a priority level for each of thewireless access interfaces that is for the neighbouring infrastructureequipment and the serving of an infrastructure equipment.

S22: If the signal reception metric (Srxlev, Squal) is above the firstthreshold associated with switching to a higher priority wireless accessinterface then processing proceeds to step S24 otherwise processingproceeds to S26. The first threshold which is associated with switchingto a higher priority in S22 is ThreshX,HighP where X=another wirelessaccess interface for a neighbouring cell or the serving cell.

S24: If the signal reception metric (Srxlev, Squal) for a higherpriority wireless access interface is above the first threshold(ThreshX,HighP) then the UE switches by reselecting the higher prioritycell which becomes the new serving cell.

S26: If the signal reception metric (Srxlev, Squal) is below the firstthreshold (ThreshX,HighP) then the UE begins to perform measurements ofany wireless access interface including neighbouring cells which have alower priority or an equal priority. The UE therefore determines thesignal reception metric (Srxlev, Squal) for lower priority cells andcompares these with the second threshold for selecting the lowerpriority cells. The second threshold in S28 is Threshseving,LowP and sois a threshold set for the serving wireless access interface to switchto a lower priority cell.

S28: If the serving cell has a signal reception metric (Srxlev, Squal)which is below the second threshold (Threshseving,LowP) for selecting alower priority wireless access interface then processing proceeds toS30. Otherwise the processing proceeds back to step S34.

S30: If the measured signal reception metric (Srxlev, Squal) for anyother wireless access interface for a neighbouring cell is above a thirdthreshold (ThreshX,LowP) for selecting one of the lower priority cellsthen processing proceeds to step S36. Otherwise processing proceeds tostep S32. The third threshold is ThreshX,LowP, where X=another wirelessaccess interface for a neighbouring cell or the serving cell.

S32: According to the present technique if one of the wireless accessinterfaces provided by the serving infrastructure equipment or the oneor more neighbouring infrastructure equipment is an enhanced wirelessaccess interface then, according to an example of the present technique,the relative priority for the enhanced wireless access interface is setto the lowest relative priority. Accordingly the UE will typicallyconsider the enhanced wireless access interface after it has consideredthe other wireless access interfaces. Therefore if the measured signalreception metric (Srxlev, Squal) for an enhanced wireless accessinterface provided by the serving infrastructure equipment of one ormore of the neighbouring infrastructure equipment is above the thirdthreshold (ThreshX,LowP) for selecting one of the lower priority cellsthen processing proceeds to step S38, otherwise processing proceeds tostep S34. As will be appreciated in an alternative representation thensteps S30 and S32 could be regarded as the same step, and steps S36 andS38 could be regarded as the same step. However to illustrate thedifferences provided by the method of selecting or reselecting accordingto the present technique then step S32 is shown as a separate step withan associated separate step S38.

S34: If the wireless access interfaces are of equal priority then the UEperforms a ranking of the relative order of priority of the wirelessaccess interfaces, which is may select as explained above. Processingthen proceeds to step S1.

S36: If the signal reception metric (Srxlev, Squal) is above the thirdthreshold (ThreshX,LowP) then the UE selects the lower priority cell asits new cell and the neighbouring cell becomes a serving cell.

S38: Similarly, if the signal reception metric (Srxlev, Squal) for theenhanced wireless access interface is above the third threshold(ThreshX,LowP) then the UE selects the enhanced wireless accessinterface, which may be provided by the serving infrastructure equipmentor one of the neighbouring infrastructure equipment as its new cellwhich becomes the new serving cell. As explained above, in analternative representation steps S36 and S38 could be considered as thesame step.

An illustration of the operation of the method according to the presenttechnique is illustrated further by the example graphical representationin FIGS. 8 and 9.

FIG. 8 illustrates an operation of the UE when reselecting to anenhanced coverage neighbour cell. The graphical plots shown in FIG. 8provide on the X-axis a representation of the signal reception metricsuch as the Srxlev and on the Y-axis time.

In FIG. 8, a first plot 801 is a graphical plot of a change in thesignal reception metric of the current or serving wireless accessinterface provided by the selected or serving infrastructure equipment.A second plot 802 provides a plot of signal reception metric of anenhanced wireless access interface which may be provided by the servinginfrastructure equipment or one or more of the neighbouringinfrastructure equipment. A third plot 803 provides the signal receptionmetric from a neighbouring wireless access interface which for thisexample is not an enhanced wireless access interface.

Compared against each of the signal plots 801, 802, 803 is a firstdashed line 804 providing a first relative threshold(ThreshX,Low/HighP). For the example showing in FIG. 8 a first dashedline 804 represents a threshold for switching to a higher prioritywireless access interface. However, for this example this alsorepresents the threshold for switching to a lower priority wirelessaccess interface. Therefore, effectively a third threshold(Threshserving) 806 is provided which is the threshold of the servingcell to switch to a lower priority cell for wireless access interface.

As can be seen in FIG. 8, the signal reception metric for the enhancedcell is above that of the neighbouring cell 803 because of the offsetwhich has been introduced into the signal reception metric to accountfor the lower signal power which is required to transmit and receivesignals for an enhanced wireless access interface. As can be seen inFIG. 8, the signal reception metric crosses the threshold for othercells 804 at a point 810. Accordingly, as reflected in step S22 in theflow diagram in FIG. 7 the UE would in the case of a normal operationswitch to the enhanced wireless access interface. However, in accordancewith the present technique the enhanced wireless access interface is setto the lowest priority level. Accordingly, the UE does not performmeasurements for this enhanced wireless access interface and thereforedoes not consider switching to this wireless access interface. Incontrast the signal reception metric for the other wireless accessinterface 803 provided by a neighbouring cell never crosses the upperthreshold (ThreshX,Low/HighP) and so even though this may have higherpriority the UE does not switch to this cell.

At a point 812 the received signal metric of the serving wirelessinterface falls below the lower threshold (Threshserving) for theserving wireless interface 806. Measurements for the lower prioritycells that is the enhanced wireless access interface on the serving orneighbouring cell or another wireless access interface on theneighbouring cells were triggered once the signal reception metric forhigher priority cells was not exceeded (steps S22 and S26 in FIG. 7).Accordingly the UE measures the signal reception metric of the enhancedwireless access interface 802 and the wireless access interface providedby the neighbour 803.

Once the signal reception metric for the serving cell falls below thelower threshold (Threshserving) for the serving cell 806 at point 812then the UE begins to compare the signal reception metrics for theenhanced wireless access interface and the wireless access interfaceprovided by the neighbours 802, 803. Thus in correspondence with stepS28 in FIG. 7 at point 812 then the test for whether the serving cellwhere signal reception metric is below the serving cell metric 806 issatisfied and processing begins at step S30 to compare the signalreception metrics for the lower priority enhanced wireless accessinterface and the neighbouring cell wireless access interface 802, 803.However, as can be seen in FIG. 8 the signal reception metric for thewireless access interface of the neighbouring cell 803 never exceeds theupper threshold (ThreshX,Low/HighP) 804 and so is not selected.Accordingly, step S30 is not satisfied so processing proceeds to stepS32. Since at point 810 in FIG. 8 the signal reception metric 802 forthe enhanced wireless access interface exceeded the upper threshold(ThreshX,Low/HighP) at point 810 then after point 812 the UE will selectthe enhanced wireless access interface in correspondence with steps S32and S38 shown in FIG. 7.

FIG. 9 provides a corresponding graphical plot for another scenario inwhich a signal reception metric for an enhanced wireless accessinterface 901, a serving wireless access interface 902 and a highpriority neighbouring wireless access interface 903 are plotted withrespect to time. Correspondingly the higher and lower thresholds(ThreshX,Low/HighP) and Threshserving 804, 806 are shown as dash linesas they have been shown in FIG. 8. According to the present technique atpoint 910 the signal reception metric for the serving wireless accessinterface falls below the lower threshold (Threshserving) for theserving cell 806. However, at this point the signal reception metric forthe higher priority neighbouring cell 903 does not exceed the upperthreshold (ThreshX,Low/HighP) associated with an alternative cell 804until point 912 and so step S22 in FIG. 7 would not be satisfied and soprocessing would be judged with respect to lower order priority cellsfrom steps S26 in FIG. 7 onwards.

In contrast therefore since the signal reception metric for the servingcell falls below the lower serving threshold (Threshserving) 910 atpoint 910, then according to the flow shown in FIG. 7 the processingflows through steps S28 and S30 and S32 to select the enhanced wirelessaccess interface at S38 because the signal reception metric 901 of theenhanced wireless access interface is above the upper threshold(ThreshX,Low/HighP) 804. However, at point 912 the signal receptionmetric for the higher priority neighbouring wireless access interfaceexceeds the upper threshold (ThreshX,Low/HighP) 804 and so the UEreselects the higher priority neighbouring wireless access interface. Atpoint 914 the enhanced wireless access interface signal reception metricfalls below the upper threshold (ThreshX,Low/HighP) 804. As such becausethe signal reception metric for the higher probability neighbouring cell903 remains above the upper threshold (ThreshX,Low/HighP) 804 thenmeasurements are not performed for the low or equal priority wirelessaccess interface. Therefore the UE does not perform any furthermeasurements unless or until the signal reception metric for the higherpriority neighbouring cell falls below the lower threshold(Threshserving) 806 or another wireless access interface with higherpriority exceeds the upper threshold (ThreshX,Low/HighP) 804.

Summary

As explained above, it has been proposed that a UE should consider cellswhich need to be used in enhanced coverage mode only when the UE is in“any cell selection” state, or in other words, the UE would need to scanall supported frequencies and bands for a suitable cell, before allowingcamping on a cell that would need to use enhanced coverage mode. Thiscan be time consuming and cause excessive power drain and mayunnecessarily delay the UE obtaining service, especially if severalEUTRAN bands are supported. It would be beneficial if the cell selectionprocedure is left unchanged, so that the UE will anyway select the bestcell on a frequency if it is suitable, and in order to ensure the UEdoes end up on the best cell (either the best enhanced coverage cell, orthe best non-enhanced coverage cell) we need to ensure that cellreselection works to prioritise the cells which do not require enhancedcoverage, as proposed in [2]. The cell measurement compared tosuitability criteria is also a convenient way to determine which mode ofoperation the UE should use as observed already in [7].

According to the present technique there is provided an arrangement inwhich cell reselection is made with the effect of prioritising thereselection to cells which can operate without coverage enhancement overcells which require coverage enhancement, and compensating for the lowerminimum suitability criteria in cell reselection. Specifically ascenario in which a UE may move from an area which can only use enhancedcoverage, to an area where one cell can operate in normal coverage modeand another can operate only in enhanced coverage mode or vice versa(from normal coverage to enhanced coverage on another cell) isaccommodated to bias the UE to select the normal coverage cell.

Embodiments of the present technique are therefore adapted to operate inthe following scenarios:

Cell supporting enhanced coverage operation should broadcast updatedsuitability criteria to support cell selection in this mode ofoperation, and imply support of this mode of operation in the cell.

The cell measurement determines whether UE should operate in enhancedcoverage mode or normal mode. If Srxlev/Squal is above Qrxlevmin/Qqualthen normal operation is required. If Srxlev/Squal is belowQrxlevmin/Qqual but above Qrxlevmin,EC/Qqual,EC then enhanced coverageoperation is used. If Srxlev/Squal is below both thresholds then cell isnot suitable for either operation.

No further modifications to the cell selection procedure. If UE findsthe best cell on a frequency is suitable because it supports enhancedcoverage, then cell reselection should ensure the UE moves to a bettercell if one is available.

Neighbour list signalling may be updated to indicate the updatedsuitability criteria of neighbouring frequencies and cells in order tosupport cell reselection in this mode of operation, and imply support ofenhanced coverage operation in the neighbouring cell/frequency.

Furthermore embodiments of the present technique can provide thefollowing adaptations to the operation of the UE:

-   -   1. The UE calculates two Srxlev (or Squal) values—one for normal        coverage mode and another for enhanced coverage mode for any        cell/frequency for which an updated Qrxlevmin,EC or Qqualmin,EC        is provided (including current frequency/cell).        -   a.            Srxlev=Q_(rxlevmeas)−(Q_(rxlevmin)+Q_(rxlevminoffset))−Pcompensation        -   b.            Srxlev,EC=Q_(rxlevmeas)−(Q_(rxlevmin,EC)+Q_(rxlevminoffset))−Pcompensation    -   2. Srxlev calculated based on the legacy Qrxlevmin is used along        with the legacy configured priority for that frequency.        Srxlevmin,EC calculated based on the updated Qrxlevmin,EC is        used along with a low priority (lower than the 8 configured        values).    -   3. UE evaluates the frequency (including current frequency)        using both priorities and both S-values, as if these were 2        separate frequencies/cells

Embodiments of the present technique can therefore provide a mobilecommunications system in which UEs make cell selection/reselection inwhich a more simple process is performed to ensure normal coverage cellsare prioritised over enhanced coverage cells without impacting orreducing the impact of signalling or cell reselection criteria (hencesimple UE implementation). Furthermore, enhanced coverage cells areselected only when nothing else is available, so a UE can operate asnormal unless out of normal coverage.

Various further aspects and features of the present invention aredefined in the appended claims.

The following numbered clauses provide further example aspects andimplementations of the present technique.

REFERENCES

-   [1] RP-130848, “New WI:Low Cost & Enhanced Coverage MTC UE for LTE,”    Vodafone, published at 3GPP TSG-RAN Meeting #60, Oranjestad, Aruba,    10-14 June, 2013.-   [2] R2-140700, “Consideration of Mobility Aspects for and MTC    Enhanced Coverage Mode Operation”, Vodafone Group, published at 3GPP    TSG-RAN WG2 #85, Prague, Czech Republic, 10-14 Feb. 2014.-   [3] R2-140327, “Cell Selection and Reselection in Coverage    Enhancement”, Huawei, HiSilicon, published at 3GPP TSG-RAN WG2 #85,    Prague, Czech Republic, 10-14 Feb. 2014.-   [4] R2-140369, “Enhanced Coverage Issues”, Sony, published at 3GPP    TSG-RAN WG2 #85, Prague, Czech Republic, 10-14 Feb. 2014.-   [5] 3GPP TS36.304.-   [6] LTE for UMTS: OFDMA and SC-FDMA Based Radio Access, Harris Holma    and Antti Toskala, Wiley 2009, ISBN 978-0-470-99401-6.-   [7] R2-140729, “Consideration on idle mode MTC UE in enhanced    coverage”, Alcatel-Lucent Shanghai Bell, Alcatel-Lucent, published    at 3GPP TSG-RAN WG2 #85, Prague, Czech Republic, 10-14 Feb. 2014.

1. A circuitry for a communications device for transmitting data to orreceiving data from a mobile communications network, the mobilecommunications network including infrastructure equipment, theinfrastructure equipment providing a wireless access interface fortransmitting signals to or receiving signals from the communicationsdevice, the circuitry comprising a transmitter configured to transmitsignals representing the data via a serving wireless access interfaceprovided by a selected infrastructure equipment to the mobilecommunications network, a receiver configured to receive signalsrepresenting the data via the serving wireless access interface providedby the selected infrastructure equipment, a controller configured tocontrol the transmitter and the receiver to select one of the wirelessaccess interfaces of the infrastructure equipment as the servingwireless access interface, wherein one or more of the selectedinfrastructure equipment or one or more neighbouring infrastructureequipment provide an enhanced wireless access interface providing afacility for transmitting or receiving signals at a lower power relativeto a wireless access interface which is not enhanced, and the controlleris configured in combination with the transmitter and the receiver togenerate a signal reception metric for each of the wireless accessinterfaces provided by the one or more neighbouring infrastructureequipment and for each of the wireless access interfaces provided by theselected infrastructure equipment, and to select or reselect one of thewireless access interfaces provided by the one or more neighbouringinfrastructure equipment or one of the wireless access interfacesprovided by the selected infrastructure equipment in accordance withpredetermined criteria based on the generated signal reception metrics.2. The circuitry for the communications device as claimed in claim 1,wherein each of the wireless access interfaces provided by the one ormore neighbouring infrastructure equipment and each of the one or morewireless access interfaces provided by the selected infrastructureequipment has a relative priority, and the controller is configured incombination with the transmitter and the receiver to compare therelative priorities of each of the wireless access interfaces providedby the selected infrastructure equipment and the one or moreneighbouring infrastructure equipment, to compare the generated signalreception metrics for each of the wireless access interfaces provided bythe selected infrastructure equipment and the one or more neighbouringinfrastructure equipment, and to select one of the wireless accessinterfaces provided by the one or more neighbouring infrastructureequipment or selected infrastructure equipment with at least one of thehighest priority and the highest signal reception metric.
 3. Thecircuitry for the communications device as claimed in claim 2, whereinthe enhanced wireless access interface is assigned the lowest relativepriority level.
 4. The circuitry for the communications device asclaimed in claim 3, wherein the controller is configured in combinationwith the transmitter and the receiver to select the one of the wirelessaccess interfaces provided by the one or more neighbouringinfrastructure equipment or the serving infrastructure, if one of theneighbouring infrastructure equipment provides a wireless accessinterface with a higher relative priority than the wireless accessinterface of the serving infrastructure equipment, and the signalreception metric of the higher priority wireless access interfaceexceeds a first predetermined threshold associated with selecting ahigher priority wireless access interface, then selecting, by thecommunications device the higher relative priority wireless accessinterface, or if the signal reception metric of the serving wirelessaccess interface is below a second predetermined threshold associatedwith selecting a lower priority wireless access interface, and one ofthe neighbouring infrastructure equipment provides a wireless accessinterface or an enhanced wireless access interface with a lower relativepriority than the serving wireless access interface of the selectedinfrastructure equipment, then to select the lower relative prioritywireless access interface or enhanced wireless access interface if thesignal reception metric of the lower priority wireless access interfaceexceeds a third predetermined threshold associated with selecting alower priority wireless access interface or enhanced wireless accessinterface.
 5. The circuitry for the communications device as claimed inclaim 1, wherein each of the wireless access interfaces provided by theone or more neighbouring infrastructure equipment and each of the one ormore wireless access interfaces provided by the selected infrastructureequipment has a relative priority, and the controller is configured incombination with the transmitter and the receiver to compare therelative priorities of each of the wireless access interfaces providedby the selected infrastructure equipment and the one or moreneighbouring infrastructure equipment.
 6. The circuitry for thecommunications device as claimed in claim 1, the enhanced wirelessaccess interface provides a facility for transmitting or receivingsignals over an extended coverage area relative to a wireless accessinterface which is not enhanced.
 7. The circuitry for the communicationsdevice as claimed in claim 1, wherein the circuitry is configured tomeasure a signal quality of the selected infrastructure equipment andthe one or more neighbouring infrastructure equipment, or measure asignal quality provided from each of the one or more wireless accessinterfaces provided from the selected infrastructure equipment and theone or more neighbouring infrastructure equipment, and determine foreach of the wireless access interfaces, the signal reception metricbased on a difference between the measured signal quality and apredetermined minimum signal quality level associated with each of thewireless access interfaces.
 8. The circuitry for the communicationsdevice as claimed in claim 7, wherein the signal reception metric forthe enhanced wireless access interface provided by the selectedinfrastructure equipment or the one or more neighbouring infrastructureequipment is derived using a predetermined minimum signal quality level,which is lower than the predetermined minimum signal quality level forthe wireless access interface provided by the selected infrastructureequipment or the one or more neighbouring infrastructure equipment whichis not enhanced.
 9. The circuitry for the communications device asclaimed in claim 8, wherein the predetermined minimum signal qualitylevel for the enhanced wireless access interface is lower than thepredetermined minimum quality level for the wireless access interfacewhich is not enhanced provided by the selected infrastructure equipmentor the one or more neighbouring infrastructure equipment by an amountwhich is commensurate with an amount by which the enhanced wirelessaccess interface provided by the selected infrastructure equipment orthe one or more neighbouring infrastructure equipment provides afacility for transmitting or receiving the signals at the lower powerrelative to the wireless access interface provided by the selectedinfrastructure equipment or the one or more neighbouring infrastructureequipment which is not enhanced.
 10. A circuitry for a communicationsdevice for transmitting data to or receiving data from a mobilecommunications network, the mobile communications network including aplurality of infrastructure equipment, each infrastructure equipmentproviding one or more wireless access interfaces for the communicationsdevice, the circuitry comprising a transmitter configured to transmitsignals representing the data, a receiver configured to receive signalsrepresenting the data, a controller configured to control thetransmitter and the receiver to select one of the wireless accessinterfaces of the infrastructure equipment as a serving wireless accessinterface, wherein the serving wireless access interface is provided bya selected infrastructure equipment, and wherein one or more of theselected infrastructure equipment or one or more neighbouringinfrastructure equipment provide an enhanced wireless access interfaceproviding a facility for transmitting or receiving signals at a lowerpower relative to a wireless access interface which is not enhanced, andthe controller is configured in combination with the transmitter and thereceiver to generate a signal reception metric for each of the wirelessaccess interfaces provided by the one or more neighbouringinfrastructure equipment and for each of the wireless access interfacesprovided by the selected infrastructure equipment, and to select orreselect one of the wireless access interfaces provided by the one ormore neighbouring infrastructure equipment or one of the wireless accessinterfaces provided by the selected infrastructure equipment inaccordance with predetermined criteria based on the generated signalreception metrics.
 11. The circuitry for the communications device asclaimed in claim 10, wherein each of the wireless access interfacesprovided by the one or more neighbouring infrastructure equipment andeach of the one or more wireless access interfaces provided by theselected infrastructure equipment has a relative priority, and thecontroller is configured in combination with the transmitter and thereceiver to compare the relative priorities of each of the wirelessaccess interfaces provided by the selected infrastructure equipment andthe one or more neighbouring infrastructure equipment, to compare thegenerated signal reception metrics for each of the wireless accessinterfaces provided by the selected infrastructure equipment and the oneor more neighbouring infrastructure equipment, and to select one of thewireless access interfaces provided by the one or more neighbouringinfrastructure equipment or selected infrastructure equipment with atleast one of the highest priority and the highest signal receptionmetric.
 12. The circuitry for the communications device as claimed inclaim 11, wherein the enhanced wireless access interface is assigned thelowest relative priority level.
 13. The circuitry for the communicationsdevice as claimed in claim 12, wherein the controller is configured incombination with the transmitter and the receiver to select the one ofthe wireless access interfaces provided by the one or more neighbouringinfrastructure equipment or the serving infrastructure, if one of theneighbouring infrastructure equipment provides a wireless accessinterface with a higher relative priority than the wireless accessinterface of the serving infrastructure equipment, and the signalreception metric of the higher priority wireless access interfaceexceeds a first predetermined threshold associated with selecting ahigher priority wireless access interface, then selecting, by thecommunications device the higher relative priority wireless accessinterface, or if the signal reception metric of the serving wirelessaccess interface is below a second predetermined threshold associatedwith selecting a lower priority wireless access interface, and one ofthe neighbouring infrastructure equipment provides a wireless accessinterface or an enhanced wireless access interface with a lower relativepriority than the serving wireless access interface of the selectedinfrastructure equipment, then to select the lower relative prioritywireless access interface or enhanced wireless access interface if thesignal reception metric of the lower priority wireless access interfaceexceeds a third predetermined threshold associated with selecting alower priority wireless access interface or enhanced wireless accessinterface.
 14. The circuitry for the communications device as claimed inclaim 10, wherein each of the wireless access interfaces provided by theone or more neighbouring infrastructure equipment and each of the one ormore wireless access interfaces provided by the selected infrastructureequipment has a relative priority, and the controller is configured incombination with the transmitter and the receiver to compare therelative priorities of each of the wireless access interfaces providedby the selected infrastructure equipment and the one or moreneighbouring infrastructure equipment.
 15. The circuitry for thecommunications device as claimed in claim 10, the enhanced wirelessaccess interface provides a facility for transmitting or receivingsignals over an extended coverage area relative to a wireless accessinterface which is not enhanced.
 16. The circuitry for thecommunications device as claimed in claim 10, wherein the circuitry isconfigured to measure a signal quality of the selected infrastructureequipment and the one or more neighbouring infrastructure equipment, ormeasure a signal quality provided from each of the one or more wirelessaccess interfaces provided from the selected infrastructure equipmentand the one or more neighbouring infrastructure equipment, and determinefor each of the wireless access interfaces, the signal reception metricbased on a difference between the measured signal quality and apredetermined minimum signal quality level associated with each of thewireless access interfaces.
 17. The circuitry for the communicationsdevice as claimed in claim 16, wherein the signal reception metric forthe enhanced wireless access interface provided by the selectedinfrastructure equipment or the one or more neighbouring infrastructureequipment is derived using a predetermined minimum signal quality level,which is lower than the predetermined minimum signal quality level forthe wireless access interface provided by the selected infrastructureequipment or the one or more neighbouring infrastructure equipment whichis not enhanced.
 18. The circuitry for the communications device asclaimed in claim 17, wherein the predetermined minimum signal qualitylevel for the enhanced wireless access interface is lower than thepredetermined minimum quality level for the wireless access interfacewhich is not enhanced provided by the selected infrastructure equipmentor the one or more neighbouring infrastructure equipment by an amountwhich is commensurate with an amount by which the enhanced wirelessaccess interface provided by the selected infrastructure equipment orthe one or more neighbouring infrastructure equipment provides afacility for transmitting or receiving the signals at the lower powerrelative to the wireless access interface provided by the selectedinfrastructure equipment or the one or more neighbouring infrastructureequipment which is not enhanced.